1. Field of the Invention
The present invention relates to a two-stage blow molding device and a two-stage blow molding method that heat a supplied preform, and blow-mold the preform into a container.
2. Description of the Related Art
A cold parison or two-stage system includes a blow molding device separately from a preform injection molding device. A preform (parison) that has been injection-molded by the injection molding device, and cooled to room temperature is supplied to the blow molding device. The blow molding device is configured so that the supplied preform is heated to the optimum blow temperature using a heating section, and blow-molded into a container using a blow molding section. The preform is continuously transferred by the heating section, and N (N is an integer equal to or larger than 2) preforms are intermittently transferred from the heating section to the blow molding section. The blow molding section simultaneously blow-molds the N preforms into N containers.
U.S. Pat. No. 7,727,454, JP-A-2000-117821, and JP-A-2007-276327 disclose a two-stage blow molding device. In U.S. Pat. No. 7,727,454 and JP-A-2000-117821, the preform is heated in an upright state in which the opening of the preform is positioned on the upper side, and the preform in the upright state is blow-molded into a container. In JP-A-2007-276327, the preform is heated in an inverted state in which the opening of the preform is positioned on the lower side, and the preform in the inverted state is blow-molded into a container. In U.S. Pat. No. 7,727,454, JP-A-2000-117821, and JP-A-2007-276327, the preform heating pitch is set to be smaller than the blow molding pitch, and the pitch is converted between the heating section and the blow molding section.
In JP-A-2000-117821 and JP-A-2007-276327, the preform is transferred between the heating section and the blow molding section by transferring a preform carrier that holds the preform. The preform carrier that has become empty is returned to the heating section, and provided with a new preform. In JP-A-2000-117821, a blow molding operation is performed in a state in which the preform carrier is positioned in an upper transfer path having a blow molding position, and inverted using an inversion device, and the empty preform carrier is returned to the heating section through a lower transfer path. In the heating section, a new preform is supplied to the inverted preform carrier. The preform carrier is then inverted using an inversion device, and the preform is heated in the upright state.
A hot parison or one-stage blow molding device is configured so that N preforms that have been injection-molded by an injection molding section are blow-molded into N containers in a state in which the preforms retain heat applied during injection molding. As disclosed in JP-B-53-22096, a typical blow molding device is configured so that an injection molding section, a temperature control section, a blow molding section, and an ejection section are provided at four positions of a turntable, and a preform or a container is rotated using a neck mold. In this case, a preform that has been injection-molded in the upright state is transferred and blow-molded in the upright state. The one-stage system is characterized in that the number of preforms that are simultaneously injection-molded coincides with the number of preforms that are simultaneously blow-molded.
The two-stage blow molding device may heat a preform in the upright state (see U.S. Pat. No. 7,727,454 and JP-A-2000-117821). In this case, since the number of transfer members for which the structure becomes complex increases as a result of continuously transferring the preform in the upright state using the heating section, the cost of the device necessarily increases. In the heating section, a plurality of rod-like heaters that extend along the preform transfer path are disposed at a different height. Since the body of the preform in the upright state decreases in diameter (i.e., is tapered) toward the bottom thereof, the preform may be uniformly heated by disposing the lower rod-like heater close to the center of the transfer path as compared with the upper rod-like heater. In this case, if the preform that is transferred in the heating section falls by accident, the preform is necessarily caught by the lower rod-like heater. Such a situation is dangerous. Therefore, the device disclosed in U.S. Pat. No. 7,727,454 or JP-A-2000-117821 that heats a preform in the upright state is not suitable for a preform (e.g., wide-mouth preform) that is formed so that the body decreases in diameter (i.e., is tapered) toward the bottom.
The above problem does not occur when using the device disclosed in JP-A-2007-276327 in which a preform is heated in the inverted state. It may be advantageous to blow-mold a preform in the inverted state into a container in the inverted state from the viewpoint of preform transfer. However, placement of equipment may become difficult from the viewpoint of blow molding since a drive mechanism for inserting a blow core mold or a stretching rod into the downward opening of the preform significantly occupies the space inside the stage. Therefore, a relatively large clamping mechanism that opens/closes and clamps a heavy blow mold and/or bottom mold cannot be disposed inside the stage. In this case, a relatively large clamping mechanism that opens/closes and clamps the blow mold and/or bottom mold must be disposed on or above the stage.